Monitoring of Insecticide Resistance to Helicoverpa Armigera (Hubner) in Cotton Growing Areas of Punjab

The monitoring of insecticide resistance was carried out during 2005 crop season in cotton growing areas of Punjab state. In Mansa and Bathinda districts, LD₅₀ values were 0.08, 0.26, 0.09, 0.98 and 0.05 μg per larva with resistance ratios of 4.2, 8.9, 1.5, 139.8 and 5.0 to chlorpyriphos, endosulfan, spinosad, cypermethrin and quinalphos, respectively. In Bathinda district, during August, LD₅₀ values were 0.07, 0.12, 0.07, 0.26 and 0.03 pig per larva aith resistance ratios of 3.6, 3.7, 1.1, 37.0 and 3.0 than in October with LD₅₀ values of 0.16, 0.25, 0.07, 1.41 and 0.07 μg per larva with resistance ratios of 8.2, 7.9, 1.2, 201.3 and 6.5 to chlorpyriphos, endosulfan, spinosad, cypermethrin and quinalphos, respectively. Cypermethrin resistance was found to be maximum (139.9 folds) in October in Mansa and Bathinda (37 folds) during August and 201 folds durrng Octoberr Other rnsecticides like chlorpyrrphos, endosulfan and quinalphos developed 3 to 9 folds resistance. Maximum level of resistance was observed to synthetic pyrethroids (cypermethrin). The population of H. armigera was susceptible to spinosad and it was most effective through out season.